# Pancreatic Schwannoma: A Rare Culprit But Accurate Diagnosis Can Avoid Resection

## TL;DR

A rare pancreatic tumor called schwannoma was accurately diagnosed using imaging and biopsy, avoiding unnecessary surgery.

## Contribution

Demonstrates how EUS-guided biopsy and immunohistochemistry can accurately diagnose pancreatic schwannomas preoperatively.

## Key findings

- Schwannoma was diagnosed via EUS-guided biopsy and confirmed by S-100 positivity and other marker negativity.
- Conservative management was successful with no tumor growth over two years of follow-up.
- Accurate diagnosis avoided unnecessary surgical resection in this case.

## Abstract

Pancreatic schwannomas are extremely rare benign tumors originating from Schwann cells of peripheral nerves, often mimicking more common pancreatic tumors, such as neuroendocrine neoplasms or solid pseudopapillary neoplasms, making preoperative diagnosis challenging. We describe a 65-year-old asymptomatic man referred for evaluation of an incidental pancreatic body mass detected by ultrasound. Laboratory findings, including liver enzymes and tumor markers (CA19-9 and CEA), were normal. Contrast-enhanced CT revealed a well-defined 20 mm mass with delayed enhancement, and MRI showed low intensity on T1-weighted images, mildly high on T2, and slight diffusion restriction. Based on imaging, a pancreatic neuroendocrine neoplasm was initially suspected. Endoscopic ultrasound-guided tissue acquisition with a 22-gauge needle was performed. Histology revealed bundles of spindle-shaped cells with mild atypia and eosinophilic cytoplasm. Immunohistochemistry was diffusely positive for S-100 protein and negative for AE1/AE3, CD34, c-Kit, and desmin, confirming pancreatic schwannoma. Given its benign nature, the patient was managed conservatively without surgery, and no tumor growth was observed over two years of follow-up. This case highlights the importance of including schwannoma in the differential diagnosis of solid pancreatic lesions and illustrates how an endoscopic ultrasound (EUS)-guided biopsy with immunohistochemistry can enable accurate preoperative diagnosis and avoid unnecessary surgical resection.